In a typical refrigeration system, particularly those found in supermarkets, a plurality of evaporators are used to refrigerate foodstuff in refrigerated display cases. Such systems basically comprise a closed circuit having a compressor stage, a condenser stage, an expansion stage and an evaporator stage. Other stages may be added to the above described basic refrigeration circuit in order to recuperate heat, or to provide refrigeration systems with defrosting loops for high speed defrosting of the evaporators. For instance, U.S. Pat. No. 5,673,567, issued on Oct. 7, 1997 to the present assignee, discloses a refrigeration system with a heat reclaim loop for recuperating heat from hot high pressure refrigerant gas outletting from the compressor stage, rather than evacuating the heat through the condensers, where the heat would be lost to the atmosphere. Thus, the heat reclaim loop is provided in parallel to the condenser stage in order to recuperate heat in heat exchange devices rather than rejecting it to the atmosphere. Preferably, in the cooler seasons, the heat is used for heating the entrance area and other specific colder areas of supermarkets. In the warmer months, the heat may be recuperated for heating water.
U.S. Pat. No. 5,826,433, issued on Oct. 27, 1998 to the present assignee, discloses modification to the above described patent, whereby a modulating valve is provided for efficiently controlling the rate of heat reclaim versus the heat rejection through the condenser stage.
Finally, U.S. Pat. No. 6,089,033, issued on Jul. 18, 2000 to the present assignee discloses a refrigeration system configuration in order to defrost evaporator units at higher speeds.
These refrigeration systems, and generally most refrigeration systems used in supermarkets, have roof top condensers in order to reject heat at the outlet of the compressor stage, whereby the refrigerant is condensed at least partially to a liquid state. Unfortunately, the loops to the roof top condensers extend the piping length of the refrigeration system. Accordingly, the piping networks of refrigeration systems are filled with refrigerant to provide every stage with the necessary conditions for refrigeration. Furthermore, with the advent of heat reclaim loops and high speed defrost cycles, even more refrigerant is used.
Unfortunately, the refrigerants typically used in such refrigeration systems (i.e. refrigerants 404, 408, 507, AZ-20 and the like) are expensive and are often volatile, whereby they may be hazardous to human health and to the environment. The more these refrigerants are used, the higher is the risk of polluting the environment.